Comparative Proteomic Analysis of Brassica napus in Response to Drought Stress

Drought
is one of the most widespread stresses leading to retardation
of plant growth and development. We examined proteome changes of an
important oil seed crop, canola (Brassica napus L.),
under drought stress over a 14-day period. Using iTRAQ LC–MS/MS,
we identified 1976 proteins expressed during drought stress. Among
them, 417 proteins showed significant changes in abundance, and 136,
244, 286, and 213 proteins were differentially expressed in the third,
seventh, 10th, and 14th day of stress, respectively. Functional analysis
indicated that the number of proteins associated with metabolism,
protein folding and degradation, and signaling decreased, while those
related to energy (photosynthesis), protein synthesis, and stress
and defense increased in response to drought stress. The seventh and
10th-day profiles were similar to each other but with more post-translational
modifications (PTMs) at day 10. Interestingly, 181 proteins underwent
PTMs; 49 of them were differentially changed in drought-stressed plants,
and 33 were observed at the 10th day. Comparison of protein expression
changes with those of gene transcription showed a positive correlation
in B. napus, although different patterns between
transcripts and proteins were observed at each time point. Under drought
stress, most protein abundance changes may be attributed to gene transcription,
and PTMs clearly contribute to protein diversity and functions.

干旱系植物生长与发育过程中最为普遍的胁迫之一。本研究对一种重要的油料作物——油菜（ Brassica napus L.）——在14天干旱胁迫条件下的蛋白质组变化进行了考察。通过iTRAQ LC–MS/MS技术，我们鉴定了在干旱胁迫期间表达的1976种蛋白质。其中，417种蛋白质在丰度上发生了显著变化，且在胁迫的第三、第七、第十和第十四天，分别有136、244、286和213种蛋白质呈现出差异表达。功能分析表明，与代谢、蛋白质折叠与降解以及信号传导相关的蛋白质数量减少，而与能量（光合作用）、蛋白质合成以及胁迫与防御相关的蛋白质数量则因干旱胁迫而增加。第七天和第十天的蛋白质谱图相似，但第十天出现了更多的翻译后修饰（PTMs）。有趣的是，181种蛋白质经历了PTMs；其中49种在干旱胁迫植物中表现出差异变化，而33种在第十天被观察到。蛋白质表达变化与基因转录变化的比较表明，在油菜中存在正相关，尽管在每个时间点转录本与蛋白质之间观察到不同的模式。在干旱胁迫条件下，大多数蛋白质丰度的变化可能归因于基因转录，而PTMs显然对蛋白质多样性和功能的实现做出了重要贡献。